[Wave 9] Expand playground smoke tests beyond the happy path

[truthixify]

Problem

The playground smoke suite verifies the guided send flow, but it does not cover invalid input, rejected signatures, wrong networks, RPC retries, or reset behavior.

Done when

• Add deterministic error-state fixtures.
• Cover wallet rejection, malformed meta-address, timeout, and retry.
• Assert that sensitive values are not rendered in errors.
• Run the expanded suite in docs CI.

[somotochukwu-dev]

@somotochukwu-dev has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi maintainer
Please I would like to work on this issue, please assign this issue to me.
Thanks

ℹ️ Repo Maintainers: To accept this application, review their application or assign @somotochukwu-dev to this issue.

[Adesam007-pr3dator]

@Adesam007-pr3dator has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi , I would love to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Adesam007-pr3dator to this issue.

[Prisca21-cloud]

@Prisca21-cloud has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi, I'd like to pick this up. I've already forked the repo and set up the dev environment, so I can start immediately.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Prisca21-cloud to this issue.

[layla242]

@layla242 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Please, can I get assigned to work on this issue, I have the experience needed to fix it

ℹ️ Repo Maintainers: To accept this application, review their application or assign @layla242 to this issue.

[drips-wave]

Congratulations, @Prisca21-cloud! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on September 30, 2026.

🧑‍💻 @Prisca21-cloud: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊